The association between digit ratio (2D:4D) and the first spermatorrhea among Chinese boys.

•We investigated the association between digit ratio (2D:4D) and the first spermatorrhea in Chinese boys.•There was no correlation between 2D:4D and the first spermatorrhea.•High prenatal androgen exposure may be directly and indirectly related to the first spermatorrhea.•High prenatal estrogen exposure may be indirectly associated with the first spermatorrhea by testosterone.•We have developed the novel index named Multiplying index of digit ratio and length (MIDRL) for the first time.